Craving for alcohol has been related to loss of control drinking and is a major target of biological and behavioral interventions for alcohol dependence. Our previous research has demonstrated that olanzapine (a dopamine antagonist) attenuates craving for alcohol, that a variant in the gene that expresses D4 receptors influences craving for alcohol, and that olanzapine is particularly effective at reducing craving among individuals with this variant. Pilot data from a recent 12week trial of olanzapine indicates that olanzapine is well tolerated and that olanzapine reduces drinking, particularly among individuals with the aforementioned genetic variant. The objective of the present application is to examine the effectiveness of olanzapine (5 mg/day), as compared to olanzapine (2.5 mg/day) and a placebo control, in terms of reducing craving and alcohol use behavior among treatment seeking alcoholics. Furthermore, the present application will examine whether the effects of olanzapine on drinking outcomes are mediated by its effects on a specific putative mechanism (i.e., cue-elicited craving for alcohol) and determine whether the DRD4 VNTR polymorphism is a marker for the effectiveness of olanzapine. To that end, 202 alcohol dependent subjects will be randomly ; assigned to medication group and receive 12 weeks of medication. Subjects will complete follow-up assessments at 3 and 6 months after the end of the treatment. It is expected that olanzapine will significantly reduce cue-elicited craving and alcohol use behavior in a dose dependent fashion over the course of the 12 week trial and follow-up period, as compared to the placebo condition. Furthermore, it is expected that the effects of olanzapine on alcohol use behavior will be mediated by the effect of olanzapine on cue-elicited craving and that the effects of olanzapine on cue-elicted craving and alcohol use behavior will be moderated by the DRD4 VNTR, such that olanzapine will be more effective among individuals with the 7 repeat allele. The successful completion of the proposed research is expected to advance a new medication for alcohol dependence and advance genetic markers that predict the effectiveness of this medication.